Synthesize retinoids for in vitro studies. The approach will involve the synthesis of small quantities of different retinoids, the choice of which will be dictated by the needs and interest of the NCI Carcinogenesis Program. In general, the contractor will: synthesize a variety of retinoids with different side chains and/or ring structures; synthesize a variety of radioactive retinoids, depending on NCI needs; provide NCI Carcinogenesis Research Program with purified compounds suitable for testing; and supply the Project Officer with data documenting the radiochemical and chemical purity of each compound and a small sample of the compound on which NCI personnel can determine the purity.